1. Field of the Invention
The present invention relates to an operation line tracking device for an industrial robot to perform an operation with a tool mounted on the robot while moving the tool along an operation line detected by a sensor such as a laser sensor.
2. Description of the Related Art
There is known an industrial robot such as a welding robot for performing an operation such as a welding operation by detecting a position of an operation line formed on an object of the operation using a sensor such as a laser sensor and moving a tool mounted on the robot to track the detected operation line.
In the tracking of the operation line, if the sensor fails to detect the operation line to cause a detection error, an operator of the robot has to seek a cause of the detection error and take a countermeasure against the detection error for restarting the tracking operation. There is known from Japanese Patent Laid-pen Publications Nos. 8-103869 and 8-103870, a method of dealing with a detection error in which the detection of the operation line is automatically repeated for predetermined times when a detection error occurs, and if the detection of the operation line is successful, the detected operation line is tracked and if the operation line is not detected in the repeated detection of predetermined times, an indication of error is displayed.
In the above conventional art as disclosed in Japanese Patent Laid-Open Publications Nos. 8-403869 and 8-103870, the detection of the operation line is repeatedly carried out automatically under the same detecting condition and it needs an operator s service to change the detecting condition. In particular, according to the above technology, when the sensor fails to detect the operation line or the position of the detected operation line largely deviates from a taught operation line, it is determined that a detection error occurs. There is a certain cause of the detection error and thus the detection of the operation line scarcely succeeds by repeating the detection under the same detecting condition. Also, in the case where the position of the detected line largely deviates from that of the taught operation line, there is a certain cause of such case and it is hard to success in detection by repeating the detection of the operation line under the same detecting condition.
Thus, it has needed an operator to take a countermeasure against the detection error, so that efficiency of the automatic tracking operation performed by the robot is lowered. Specifically, an optimal detecting condition for detecting an operation line on workpieces varies depending on a surface condition and a shape of the workpieces. For example, a detection error may occur in various cases where a region of low reflectance exists on the surface of the workpiece or a region of high reflectance because of oil, etc. exists on the surface, variations of the position/posture of the workpiece is large, a scanning range of the sensor is too wide to detect an unexpected object to fail in detection, a shape of the workpiece changes to require a change of the detecting condition. In the above cases, a detection error can not be eliminated unless the detecting condition is changed. As discussed, the change of the detecting condition has been performed by an operator manually, requiring a number of processes for recovering the automatic operation, so that an efficiency of the automatic operation of the robot is lowered.
The present invention provides an operation line tracking device for a robot to perform an operation with a tool mounted on the robot while moving the tool along an operation line formed on an object of operation. According to one aspect of the present invention, the operation line tracking device comprises a detector to detect a position of the operation line with a sensor under a preset detecting condition; observing means to observe detection state of the operation line by the detector; and detecting condition changing means to automatically change or reset the preset detecting condition based on the detection state observed by the observing means.
According to another aspect of the present invention, the operation line tracking device comprises: a detector to detect a position of the operation line using a sensor mounted on the robot under a preset detecting condition; operation stopping means to stop the operation of the robot and the detection of the operation line when the detector fails to detect the operation line; detecting condition changing means to change or reset the preset detecting condition after the detection of the operation line is stopped; operation restarting means to restart the detection of the operation line under the changed or reset detecting condition, and restart the operation of the robot when the detector succeeds in detecting the operation line under the changed or reset detecting condition.
The sensor of the detector may comprise a laser sensor operating under a preset laser output intensity, and the detecting condition changing means may change or reset the preset laser output intensity.
The detecting condition changing means may change or reset a detecting orientation and/or a detecting position of the sensor with respect to the object of operation.
The detector may detect a position of the operation line using a preset operation line detection program, and the detecting condition changing means may change or reset the preset operation line detection program for another operation line detection program. In this case, the detecting condition changing means may have a memory storing operation line detection programs with different detection algorithms, and selects one of the operation line detection programs as the preset operation line detecting condition and selects an operation line detection program other than the preset operation line detection program after the detection of the operation line is stopped.
The sensor of the detector may comprise a visual sensor for sensing an image of the object of operation within a preset visual field and the detecting condition changing means changes or resets the preset visual field of the visual sensor. In this case, the sensor may have a laser beam scanner for scanning a preset scanning region on the object of operation, and the detecting condition changing means may change or reset the visual field by changing the preset scanning region.
The operation line tracking device of the present invention may comprises analyzing means to analyze a cause of a detection failure when the detector fails in detecting the operation line, and the detecting condition changing means may automatically change or reset the preset detecting condition in accordance with the cause of the detection failure analyzed by the analyzing means.
The operation restarting means may restart the operation of the robot at a preset position different form the stopped position of the operation of the robot.
An alarm message may be displayed on a display device when the detector fails in detecting the operation line for a predetermined time or times under the changed or reset detecting condition.
At least one of information on the occurrence of the detection failure, information on the stop position of the operation of the robot, information on the detecting conditions before and after the changing or resetting of the detecting condition is stored in a memory when the detection of the operation line is restarted, and the information stored in the memory may be displayed on the display device.